1. Field of the Invention
The invention relates to an apparatus for microwave irradiation of materials.
2. Description of Related Art
From DE-OS 32 24 114 an apparatus of this kind is known which serves for heating liquids and in particular for cracking used oil that flows through pipelines including a cracking pipe of oxide ceramic or of similar non-polar materials and is heated by microwave irradiation up to temperatures of about 700.degree. C. and is thereby fractionated. To generate the microwave radiation a number of so-called power packets are arranged along the cracking pipe.
This known apparatus is disadvantageous insofar as its use is restricted to the heating of polar liquids by direct irradiation thereof with microwaves, and a change in the degree to which the liquid is heated cannot be effected without a corresponding change the radiation dose applied to the liquid.
Described in U.S. Pat. No. 3,805,009 is an apparatus for acting on foodstuffs with microwaves, during frying in an oil bath. In this known apparatus the foodstuffs are conveyed on a horizontal circulating conveyor belt under a microwave application chamber through the provided heating zone. A plurality of antennas in the form of rods extending transversely are provided in the middle region of the application chamber. Arranged before and after the antennas in the application chamber are material layers arranged one above the other of which the upper layer consists of a microwave absorbing material, while the lower layer consists of a dielectric material such as Pyroceran. The purpose of the layered arrangement is to reduce or restrict the application of microwaves to the foodstuffs.